I need to buy an iPhone5—and I would like to know what is the best company for coverage, and price for Portland OR and Silicon Valley...?

I have been using AT&T and hate the company because of numerous service and pricing issues. I am presently living in Palo Alto, CA and the cell service is spotty here; but moving next month to Portland. What company should I switch to that sells the Iphone 5 and has a cell service that IS GOOD IN THESE AREAS, good for data surfing on the web, phone calls an texts…and that has good coverage at least in the silicon valley, CA and Portland OR area?